One-way radio connection scheme designed with TXL2 and RXL2

The TXL2 and RXL2 modules are 9600baud simplex multi channel OEM radio modems in a Radiometrix SIL standard footprint, operating on European 433MHz ISM band. They provide one-way radio connection solutions. The TXL2/RXL2 is compatible with EN 300 220-3 and EN 301 489-3. It has a high-quality stable reference crystal and a low-noise synthesizer/VCO, as well as a SAW front-end filter and a multi-stage ceramic IF filter. The transmit power is +10dBm and the receive sensitivity is -107dBm. It is mainly used in handheld terminals, PDAs, industrial telematics, building environment detection and control, remote data acquisition systems, ships, automotive data acquisition, etc. This article introduces the main features, indicators and block diagrams of TXL2 and RXL2, as well as the block diagram of direct connection with MCU and the block diagram of connecting to RS232 port through RS232 line driver/receiver

. 433MHz ISM band. The TXL2/RXL2 pair act as a transparent serial cable to attached host. Unlike raw FM radio modules (eg TX2A/RX2A), TXL2/RXL2 will take care of preamble, synchronization, bit balancing and error checking along with automatic noise squelching.

The TXL2/RXL2 pair provides a one-way radio link. Provided no two devices attempt to transmit simultaneously no further restrictions on data transmission need be made, as all transmit timing, valid data identification and datastream buffering is conducted by the units. Synchronization and framing words in the packet prevent the receiver outputting garbage in the absence of wanted RF signal or presence of interference.

For multiple radio systems a TXL2/RXL2 can be set to 1 of 8 unique addresses. As well as having unique addresses, the TXL2/RXL2 allow operation on one of 5 pre-set frequencies in the 433MHz band. These frequencies are non-overlapping and simultaneous operation of TXL2/RXL2 pairs in the same area on different channels will be possible. Units are supplied on 433.925MHz (Ch0) as default

TXL2/RXL2 Main features:

Conforms to EN 300 220-3 and EN 301 489-3

High quality, stable crystal reference

Low noise synthesizer / VCO

SAW front-end filter

Multi-stage ceramic IF filtering

Single conversion superhet

Serial modem baud rate at 9600bps (simplex)

Addressable point-to -point

5 serial select wideband channels

TXL2/RXL2 main technical specifications:

Operating frequency: 433.925MHz (default)

Modulation: 16kbps bi-phase FSK

Supply: 5V at 28mA transmit, 22mA receive/idle

Transmit power: +10dBm (10mW)

Receiver sensitivity: -107dBm (for 1% BER)

32 byte data buffer

Adjacent channel rejection: 6 0db@ ±320kHz

Receiver Blocking: >75dB

TXL2/RXL2 Applications :

Handheld / portable terminals

PDAs, organisers & laptops

Industrial telemetry and telecommand

In-building environmental monitoring and control

Remote data acquisition system, data logging

Fleet management, vehicle data acquisition

Figure 1.TXL2 block diagram

Figure 2.RXL2 block diagram

Figure 3.TXL2 and RXL2 direct connection block diagram with MCU

Figure 4. Block diagram of TXL2/RXL2 connected to RS232 port via RS232 line driver/receiver